1. Field of the Invention
The present invention relates to a clamping apparatus adapted to clamp an object to be clamped or fixed (referred to as a fixed object hereinafter) such as a metal mould, a work pallet, a work piece and the like onto a fixed angular table of a processing machine such as an injection moulding machine, a machining center and so on by means of a fluid pressure such as a pressurized air, a pressurized oil and the like, and more specifically to a technology intended to obtain a strong clamping force by use of a wedge type force increasing mechanism.
2. Description of the Related Arts
Such a clamping apparatus provided with the wedge type force increasing mechanism is described in U.S. Pat. No. 4,365,792. This clamping apparatus having a conventional construction operates as follows.
Firstly, when a piston is advanced a distance of an extension stroke, a clamping member is advanced from a retracted position to an extended position. Then, when the piston is advanced a distance of a temporary clamping stroke, a wedge member is advanced relative to the clamping member at the extended position. Thereupon, the clamping member is swung by the wedge member from the extended position to a temporary clamping position so as to be brought into contact with a metal mould (referred to merely as a mould hereinafter). Subsequently, when the piston is further advanced a distance of a practical clamping stroke, the clamping member is strongly swung for clamping by a wedgewise engaging force of the wedge member from the temporary clamping position to a practical clamping position.
There are, however, the following problems associated with the above-mentioned conventional construction.
It is necessary for the clamping apparatus to have the temporary clamping stroke between the extension stroke and the practical clamping stroke. Since the swinging of the clamping member to the temporary clamping position is effected by the tapered wedge member, a comparatively long stroke is required for that temporary clamping stroke. Therefore, the entire stroke of the clamping apparatus becomes long. Consequently, a length of a housing in the forward and backward direction becomes large, so that the clamping apparatus becomes large in size.
Further, since the entire stroke of the clamping apparatus is long, also a clamping operation time becomes long and an efficiency of the clamping working is diminished.